[Elecraft] K3 PA3000.. you can dream, can't you?

[Jeff Wandling W7BRS]

I think this thread may have already boosted itself out of the Elecraft 
orbit, so excuse this additional post and I'll take it off line.  I don't 
know why I even started it here on this list, but the caffeen was probably 
clouding my judgement.

I'm not sure about the same cost.  Maybe there were some things I 
overlooked in the schematic and the posting earlier but the main thing is 
solid-state PA's are current devices.. Lots of current.

That one they were based on required 100Vdc @30A.  That's tough business 
to bring up cheaply, AFAIK.

It's one of the reasons why I was talked-out of starting with solid-state 
PA's for homebrew at that power level until I get my feet wet with some 
15-50W designs (many ARRL books referenced here).  I'm going to try some 
tube amps first, get a feel of building the input tuning network and so 
forth, undersanding Q, and those subsystems that are required.

After checking with MicroSemi who makes the ARF line, those particular BeO 
MOSFETS are quite expensive, new.  And the BeO makes them tricky to work 
with safely.  For a reference design, check out ARRL.org, search QEX, 
Tokyo, MOSFET keywords and you'll find the QEX article from 2006 from the 
THP designers.

For those so inclined and experienced to do so, it would be an incredible 
project -- especially the STAMP programming and so forth to make the unit 
really stand out.

The Hayward book on SS design and it's sequel are really interesting 
reading too.  I have a spare pair of 2SC2782's in bag just waiting for my 
own outboard PA homebrew project one of these days.

-jeff

On Wed, 11 Feb 2009, Rick Dettinger wrote:

> With that kind of drive requirement, you could skip the 100 watt amp on the 
> K2 or K3 and go directly to about 700 watts out using the QRP versions for 
> about the same cost.
>
> 73
> Rick   K7MW
> LaConner, WA
>
>
> On Feb 11, 2009, at 1:38 PM, Greg - AB7R wrote:
>
>> If interested there's a guy named Yuri near Seattle who has a board with 12 
>> MRF-
>> 150s on it that he tested I think with 25W drive for 1.1KW output.  I don't 
>> recall
>> what the power supply was.  Think he wanted something like $350 for it. 
>> Add may
>> still be on QRZ.com.
>> 
>> 
>> -------------------------
>> 73,
>> Greg - AB7R
>> Whidbey Island WA
>> NA-065
>> 
>> 
>> On Wed Feb 11 13:09 , Jeff Wandling W7BRS  sent:
>> 
>>> 
>>> Fun stuff -
>>> 
>>> I'm not quite looking for the KPA1000, but this is where I'd ultimately
>>> like to go design and homebrew-wise if I could try, someday.. maybe.
>>> 
>>> (I saw QEX had an article Oct/2006 for a tokyo-style amp - these hams
>>> based theirs on that design)
>>> 
>>> http://www.mods-ham.com/03_Home-brew/Homebrew-Mods/ARF1500-PA/ARF1500PA.pdf
>>> 
>>> and a follow up:
>>> 
>>> http://www.mods-ham.com/03_Home-brew/Homebrew-Mods/ARF1500-PA/ARF_PA_DL6JI.pdf
>>> 
>>> hosted at:
>>> 
>>> http://www.mods-ham.com/03_Home-brew/Homebrew_Frame.html
>>> 
>>> Auf Deutsch. Select all the text, paste it into various translators
>>> online and get a jist of what's going on.
>>> 
>>> -jeff
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